The present invention relates to a microfluidic component comprising a substrate having a channel for leading individual particles through for sorting particles in a fluid flow, in particular a liquid flow, and also a method for sorting particles.
The manipulation of suspended particles is generally known and is described, for example, by G. Fuhr et al in “Naturwissenschaften” [Natural sciences] volume 81, 1994, page 528 ff. Here, the suspended particles can be any desired particles or else biological cells. In the following text, therefore, in general only particles will be mentioned. The microsystems form in particular channel structures through which a suspension liquid with the particles to be manipulated flow. In the channel structures, microelectrodes are fitted to the channel walls and have high-frequency electric fields applied to them. Under the action of the high-frequency electric fields between two electrodes, polarization forces are produced in the suspended particles on the basis of negative or positive dielectrophoresis, said forces permitting repulsion or attraction by the electrodes and, in interaction with flow forces in the suspension liquid, permitting manipulation of the particles in the channel. Electrodes of this type are described, for example, in WO 00 00 293.
In S. Gawad et al, “1st Annual International IEEE-EMBS Special Topic Conference on Microtechnologies in Medicine & Biology Oct. 12-14, 2000, Lyons, FRANCE:”, pages 1 to 5, and also from S. Gawad et al “Lab on a Chip”, 2001, 1, pages 76 to 82, it is known to analyze cells in a microchannel by means of impedance spectroscopy. In this case, use is made of electrodes embedded in the channel, so that at least two field areas are produced, in which an impedance measurement is carried out. Evaluation is then carried out by means of a difference measurement, for example by means of a measuring bridge. With regard to further details, reference is made to these publications and the explanations given therein relating to the measuring principle and to the prior art.
The results of such an analysis can then be used to carry out cell sorting next. Here, it is likewise known to carry out cell sorting on the basis of dielectrophoresis. For example, it is known from U.S. Pat. No. 4,326,934 to extract sulfur from oil by means of dielectrophoresis.
U.S. Pat. No. 5,489,506 discloses a method and an apparatus for the continuous sorting of living cells from a mixture, in which the cells passing one or more electrodes are sorted out in accordance with their size, physical construction, chemical composition and electronic characteristics, the electrodes being connected to radio-frequency generators.
In the method described above, the different electrophoretic characteristics for the particles are used to lead these out of the fluid flow. This is passive sorting, since a specific decision as to whether the particles are to be led out or not cannot be made.
The previously known devices for characterizing particles, in particular biological cells, sorting and counting (cytometers) are distinguished by very complicated devices, which generally comprise an optical analysis device based on FACS (fluorescence-activated cell sorting) or a combination of optical and electrical measuring devices. Purely electrical detection and sorting is not carried out. Therefore, in the case of these devices, additional preparation of the particles for the optical analysis is required. This makes the analysis by means of such devices complicated and time-consuming.
It is an object of the present invention to provide an electrical flow cytometer which, on a substrate in micro- or nanotechnology, permits the identification and counting and sorting as quickly and accurately as possible.